The rapid development and wide applications of electronic paper (E-paper) displays come about as a result of the progress in semiconductor manufacturing processes, display technologies, industrial designs and communication technologies. In an electronic paper display, due to the effect of parasitic capacitance occurring in thin film transistors (TFTs) of a pixel circuit, the coupling to a variable voltage of a corresponding scan line makes the pixel voltage shift toward a negative voltage level. The pixel voltage offset (Δ V) is referred to as a feedback voltage of the pixel circuit, and the voltage value of the feedback voltage can be used as a reference for setting a common voltage (Vcom) or is directly adopted as a common voltage.
However, the detection of the feedback voltage of a pixel circuit today still largely relies on a manual manner; that is, an operator on a manufacturing line has to use a multitester to detect the feedback voltage of the pixel circuit and then read the voltage value of the feedback voltage from the multitester. So, this manual detecting and reading process not only is time-consuming but also may lead to misreading.